In semiconductor memory device, current supply to a memory cell is switched by a vertical thin film transistor, for example. This vertical thin film transistor is required reduction of the ON-resistance.
It is possible to expand a width of the channel formed in a contact area in a gate electrode and a semiconductor layer, as an example of a method for reducing the ON-resistance mentioned above. As a method for expanding the width of the channel, it is possible to expand a width of the semiconductor layer, for example. However, in this case, a space for forming a gate electrode is small, thereby the forming performance of the gate electrode may worsen.